Method for improving the colour fastness of textile material made of plastics

ABSTRACT

The invention relates to a method for improving the colour fastness of textile material made of plastics, whereby one or more vat dyes are applied to the textile material which undergoes heat treatment on its own or combined with other dyes/pigments. The material undergoes at least one additional heat treatment in connection with the colour thereof.

[0001] The present invention relates to a method of improving thecolorfastness of textile materials made of synthetics.

BACKGROUND INFORMATION

[0002] Synthetic materials are not adequately dyed by the traditionaldyeing methods. Problems occur with polyesters (PES), polyamides (PA),polyurethanes (PU) and other synthetics in particular when the textilematerial is composed of a blend of different synthetics, e.g., PA andPES. Additional problems occur when dealing with microfibers. Therefore,there has been a search for possibilities which yield good dyeing ofindividual synthetics and blends and also have high use fastness valuessuch as washfastness and lightfastness.

[0003] European Patent 0 772 709 B1 describes a method of dyeingmaterials made of synthetics using vat dyestuffs, which yields greatlyimproved washfastness and lightfastness in comparison with older methods(Thomas Vickerstaff, The Physical Chemistry of Dyeing (1968), 2^(nd)edition, page 479), and the method described there includes thefollowing steps:

[0004] a) Selecting a vat dyestuff

[0005] b) Treating the material with the dyestuff in the presence of areducing agent and an alkali, where the alkali has a concentration ofmore than 0.2 mol/L and

[0006] c) Oxidizing the treated material produced in step b).

[0007] The disadvantage of this method is that the large quantities ofalkali required result in a substantial wastewater load and high processcosts. In the case of fiber materials containing PES, e.g., PA/PESblends, the large amounts of alkali used may also result in damage tothe PES fiber and thus a considerable loss of tensile strength.

EXPLANATION OF THE INVENTION

[0008] The object of the present invention is to provide a method whichyields good colorfastness results—in particular lightfastness—as well ascausing only a minor loss of tensile strength by working with smallerquantities of alkali, in particular in the case of material made of PESand/or PA.

[0009] According to the present invention, this object is achieved by amethod as defined in the preamble in which the material is exposed to atleast one additional heat treatment following its dyeing.

[0010] This method preferably involves the heat treatment beingperformed in a dry atmosphere for a period of 0.1 sec to 60 min attemperatures between 50° C. and 300° C.

[0011] As an alternative, the process may be carried out by performingthe heat treatment in the presence of moisture for 0.1 sec to 60 min, attemperatures between 50° C. and 300° C.

[0012] The heat treatment is performed for a period of time from 0.1 secto 2 min at temperatures between 100° C. and 250° C.

[0013] The additional heat treatment is preferably performed duringtreatment steps such as embossing, finishing or make-up of the material.

[0014] The additional heat treatment is preferably applied to a materialcontaining microfibers or made entirely of microfibers.

[0015] The additional heat treatment is preferably applied to a materialmade of a nonwoven, in particular a material made of PA and/or a mixtureof PA and PES fibers and/or microfibers.

[0016] In this way the colorfastness, in particular the lightfastness ofthe dyeings is greatly increased, as shown by the following examples. Atthe same time, in comparison with the known dyeing method, samplesobtained in dyeing polyester fibers show only a comparatively minor lossof tensile strength.

[0017] Microfibers or microfilaments in the sense of this patentapplication are understood to be those having a titer of <1 dtex.

[0018] The present invention is explained below on the basis of fiveexamples. The results of the evaluation of colorfastness aresubsequently summarized.

EXAMPLE 1

[0019] A microfilament nonwoven made of 35 wt % PA and 65 wt % PES isdyed in a one-step exhaust method using the vat dyestuff indicated inTable 1 (3% dyestuff used, based on the fiber weight). For this purpose,the vat dyestuff is dispersed together with 1 g/L of the dispersantDekol® SN and 0.5 g/L of Trilon® TA, a chelating agent. The bath ratiois 1:20. It is first heated to 80° C., then pigmented for 20 minutes atthis temperature. Vatting is performed with 20 mL/L NaOH (32 wt %) and 8g/L hydrosulfite. After vatting, dyeing is continued for 30 minutes at80° C., then it is cooled to 50° C. and rinsed. Oxidation is performedat a bath ratio of 1:20 using 5 mL/L hydrogen peroxide (30 wt %) for 15minutes at 60° C. followed by saponification at 70° C. with 2 g/L sodaand 1 g/L Kieralon® B. After drying, heat treatment is performed for 1minute at 180° C. on the tenter frame.

EXAMPLE 2

[0020] A microfilament nonwoven made of 35 wt % PA and 65 wt % PES isdyed in a one-step exhaust dyeing process using a mixture of thedispersed dyes and vat dyes listed in Table 2. Both the disperse dye andthe vat dye are dispersed together with 1 g/L of the dispersant Dekol®SN and 0.5 g/L of the chelating agent Trilon® TA and then the pH isadjusted to 4.5 to 5 using acetic acid. The bath ratio is 1:20. Dyeingis performed at 130° C. for 45 minutes. Then the bath is cooled to 80°C. and vatting is performed using 12 mL/L NaOH (32 wt %) and 6 g/Lhydrosulfite with the addition of 20 g/L of Glauber's salt. Aftervatting, dyeing is continued for 30 minutes at 80° C., then cooling to50° C. and rinsing. Oxidation is performed at a bath ratio of 1:20 using5 mL/L hydrogen peroxide (30 wt %) for 15 minutes at 60° C. followed bysaponification at 40° C. with 2 g/L soda and 1 g/L Kieralon® B. Afterdrying, heat treatment is performed for 1 minute at 150° C.

EXAMPLE 3

[0021] A printing paste containing 800 g/L of a stock paste of 600 g/Lstarch ether thickener, 50 g/L Glyezin® A, 100 g/L potash and 100 g/LRongalit C+20 g/L of the vat dyestuff Indanthrene® Yellow T-5GF and 180g/L water is applied with a doctor blade to a microfilament nonwoven of35 wt % PA and 65 wt % PES, dried at 98° C., fixed for 10 minutes at102° C. with saturated steam. The dyeing is then rinsed and oxidized for15 minutes at 60° C. with 5 mL/L hydrogen peroxide (30 wt %) andsaponified at 70° C. with 2 g/L soda and 1 g/L Kieralon® B. Afterdrying, embossing is performed at 240° C. using a calender.

EXAMPLE 4

[0022] A microfilament nonwoven having a weight of 100 g/m² containing35 wt % PA and 65 wt % PES is pad dyed at room temperature using a vatcontaining 100 g/L of the vat dyestuff Indanthrene Direct Black RB,dried at 120° C. and then developed by a saturated steam treatment for 1minute at 103° C. using 60 g/L NaOH (50 wt %) and 80 g/L hydrosulfite(bath uptake 100%). Oxidation is performed using 10 mL/L hydrogenperoxide (50 wt %) at a bath ratio of 1:20. At the same time 3 mL/Lacetic acid (60 wt %) is used for neutralization. Then saponification isperformed at 70° C. using 2 g/L soda and 1 g/L Kieralon® B. Afterdrying, heat treatment is performed for 1 minute at 200° C.

EXAMPLE 5

[0023] A microfilament nonwoven made of 35 wt % PA and 65 wt % PES isdyed in a one-step exhaust dyeing method with 6.6% (based on the fiberweight) of the vat dyestuff C.I. Vat Black 27 at a bath ratio of 1:57.

[0024] First it is heated to 95° C., then pigmenting is performed atthis temperature for 20 minutes.

[0025] Vatting is performed with 25 mL/L NaOH (32 wt %) and 9 g/Lhydrosulfite.

[0026] After vatting, dyeing is continued for 45 minutes at 95° C., thencooling to 50° C. and rinsing and oxidizing and saponifying as describedin Example 1.

[0027] After drying, heat treatment is performed for 1 minute at 180° C.in a tenter frame.

COMPARATIVE EXAMPLE

[0028] According to Example 3 of European Patent 0772709 B1, themicrofilament nonwoven described in Example 5, containing 35 wt % PA and65 wt % PES, was dyed with C.I. Vat Black 27. A sample of nonwoven (1.5g) was treated for 45 minutes at 95° C. in an aqueous solution of C.I.Vat Black 27 (2 mL of a 5% aqueous solution), sodium hydroxide (10 mL ofa 4M aqueous solution), Rongal HT (3 g) and water (60 mL). The treatedsample was rinsed, oxidized by treating it with 75 mL of an aqueoussolution of potassium dichromate (1.5 g) and acetic acid (15 g) for 30minutes at 65° C., then rinsed and washed with 75 mL of an aqueoussolution containing soap flakes (3.75 g) in boiling water for 10minutes.

[0029] After the process described here without a heat aftertreatment,the lightfastness and tensile strength values listed in Table 5 areobtained.

[0030] The results obtained for the lightfastness are summarized in thefollowing tables: TABLE 1 Indanthrene ® Ruby R Indanthrene ® Orange GRWith heat With heat treatment treatment No heat 1 min at No heat 1 minat treatment 180° C. after treatment 180° C. after Example 1 afterdyeing dyeing after dyeing dyeing Lightfastness 5 6 5-6 7-8 EN ISO 105B02

[0031] TABLE 2 1% Dianix Red AM-B 3% Indanthrene ® Red FFB No heat Withheat treatment after treatment 1 min at Example 2 dyeing 150° C. afterdyeing Lightfastness 5 6 EN ISO 105 B02

[0032] TABLE 3 Indanthrene ® Yellow T-5GF No heat With heat treatmenttreatment after (embossing) at Example 3 dyeing 240° C. after dyeingLightfastness 6 6-7 EN ISO 105 B02

[0033] TABLE 4 Indanthrene ® Direct Black RB No heat With heat treatmentafter treatment 1 min at Example 4 dyeing 200° C. after dyeingLightfastness 4 5 EN ISO 105 B02

[0034] TABLE 5 C.I. Vat Black 27 With heat treatment 1 min at 180° C.after Comparative Example 5 dyeing Example Lightfastness 5-6 5-6 EN ISO105 B02 Maximum tensile 229.5 N 95.3 N strength EN20073, part 3

[0035] Lightfastness according to EN ISO 105b02: score 1=very bad,8=very good

What is claimed is:
 1. A method of improving the colorfastness oftextile material manufactured from synthetics in which the textilematerial is exposed to a heat treatment when applying one or more vatdyestuffs alone or in combination with other dyestuffs/pigments, whereinthe material is exposed to at least one additional heat treatmentfollowing its dyeing.
 2. The method as recited in claim 1, wherein theheat treatment is performed in a dry atmosphere for a period of timefrom 0.1 second to 60 minutes at temperatures between 50° C. and 300° C.3. The method as recited in claim 1, wherein the heat treatment isperformed in the presence of moisture for 0.1 second to 60 minutes attemperatures between 50° C. and 300° C.
 4. The method as recited in oneof claims 2 or 3, wherein the heat treatment is performed for a periodof time from 0.1 second to 2 minutes.
 5. The method as recited in one ofclaims 2 or 3, wherein the heat treatment is performed between 100° C.and 250° C.
 6. The method as recited in one of claims 1 through 5,wherein the additional heat treatment is performed in treatment stepssuch as embossing, finishing or make-up of the material.
 7. The methodas recited in one of claims 1 through 6, wherein the additional heattreatment is applied to a material containing microfibers.
 8. The methodas recited in one of claims 1 through 6, wherein the additional heattreatment is applied to a material made entirely of microfibers.
 9. Themethod as recited in one of claims 7 through 8, wherein the additionalheat treatment is applied to a material made of a nonwoven.
 10. Themethod as recited in one of claims 1 through 9, wherein the additionalheat treatment is applied to a material made of PA and/or a blend of PAand PES fibers and/or microfibers.